Hi i have a 2000 pontiac bonneville ssei. The car was sitting in the driveway just runningsplutter as if it ran out of gas an cut off. Turns over fine but wont start. Replaced battery a couple days later and starter fine. Let it run for about a half hour then cut off. The next morning i go to start the car and it cranks. Let the vehicle sit and run for about another half hour

Hi i have a 2000 pontiac bonneville ssei with around 170k..The car was sitting
in the driveway just running when it began to splutter as if it ran out of gas an
cut off. Turns over fine but wont start. Replaced battery a couple days later
and starter fine. Let it run for about a half hour then cut off. The next morning i
go to start the car and it cranks. Let the vehicle sit and run for about another
half hour  when it began to splutter again before it cut off. Car wont start.
Someone said it was the alternator, go and had it checked out and it works
fine. As the alternator gets put back on the car i try and start it..It cranks right
up. I drove the car around maybe 3.5 miles before returning home. Turns the
car off and immediatlt right back on it starts with no problem. Maybe a half
half later i return to try and run an errand and the car doesnt start, turns but
wont start